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Three-prong vs. two-prong outlet

OutletModern receptacles now have three slots for safety purposes. This wasn’t common practice many years ago so some older homes may have receptacles with only two slots, which calls for an upgrade. But why? What does that third slot do? Does it really improve safety?

The simple answer is yes.

The slot on the left is a neutral and is a bit larger than the right one. The right slot is the hot wire, and the bottom (third) slot is the ground and is partially rounded. When an appliance is plugged in, power flows from the hot slot on the right, through the appliance’s motor, and back through the neutral slot on the left. The third ground slot will protect you from electrical shock if you’re running an appliance that has a metal-encased power supply. That metal could conduct electricity. The third prong will allow the current to ground out at the receptacle instead of through you, causing a potentially fatal shock.

Yes, there are cheater plugs that allow you to use a three-prong appliance with a two-slot outlet, but this is dangerous. The appliance will still work, but you’ve now taken away the safety feature of that third prong.

So why do some appliances only have two prongs if three is safe? The third ground prong may not be required if the appliance is sufficiently insulated. Meaning there is enough protection within the device that you won’t receive an electrical shock if you touch the appliance. This is common with lighter loads, like lamps. Appliances with a heavy load, like a dishwasher, requires the third ground prong.

Replacing old outlets with modern three-slot outlets is simple for a licensed electrician. It’s best to be on the safe side and call for help if you notice there are still two-slot outlets in your home or business.


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